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apologetics

Among Roman Catholic writers, John Henry Newman’s
An Essay in Aid of a Grammar of Assent (1870) offered a major intellectual justification of the act of faith during what he viewed as a revolutionary, seismic period in the world of ideas. Modern Catholic scholars have made contemporary apologetics a component in the subdiscipline of “fundamental theology.”

discussed in biography

...In 1870 he expressed opposition to a definition of papal infallibility, though himself a believer in the doctrine. In the same year, he published his most important book of theology since 1845,
An Essay in Aid of a Grammar of Assent (commonly known as
The Grammar of Assent), which contained a further consideration of the nature of faith and an attempt to show how faith can...